1. Field of the Invention
This invention relates to treatment of low-tension glaucoma by topically administered medications and more particularly to treatment of low-tension glaucoma by topical administration of calcium channel blocking agents.
2. Description of the Prior Art
Low-tension glaucoma is an ophthalmic condition in which the symptoms and ophthalmic pathology, i.e., loss of visual fields, loss of visual acuity and contrast sensitivity, cupping of the optic disk, etc., are present in the eye, but the intraocular pressure (IOP) is normal or only slightly elevated. It is distinguishable from primary open angle glaucoma, which is characterized by an elevated IOP. The etiology of the disease is not well understood and consequently there is no consensus as to a medicinal course of therapy. While available topical therapy may lower IOP, it is not been conclusively demonstrated to alter beneficially the course of the disease.
Consequently, certain topical medications have been used in an attempt to delay the progression of ophthalmic deterioration or even partially reverse the course of the disease. Nevertheless, conventional ophthalmic medications that lower the IOP have been used in an attempt to maintain the IOP as low as possible, even somewhat below the range usually considered as normal. Systemic drugs that increase the blood flow to the optic nerve head and/or retina have been found to have some effect in alleviating the loss of visual function in low-tension glaucoma. In particular, systemic, e.g., oral, administration of calcium channel blocking agents has been found on occasion to be of benefit in low-tension glaucoma. However, the systemic administration of vasoactive drugs in order to treat a condition of the optic nerve head and/or retina is subject to the evident disadvantage that it is difficult to attain sufficient ocular concentration without inducing systemic adverse side effects. Hitherto it has not been known to increase blood flow to the optic nerve head and/or retina and thereby arrest or alleviate the deterioration associated with low-tension glaucoma by topical administration of drugs to the eye.
Although it is well known to apply topical medications to treat ophthalmic disorders caused by dysfunction of tissues in the anterior region of the eye, topical application of medication has not been generally found effective to treat ophthalmic pathologic conditions of tissues and structures located in the posterior segment of the eye.
Accordingly, a need has continued to exist for a method of treating low-tension glaucoma by topical administration of an effective ophthalmic medicament.